1. Field
The present invention relates generally to a surface plasmon polariton (SPP) and, more particularly, to a plasmonic device.
2. Description of Related Art
A plasmon refers to a quasiparticle that is used to treat free electrons present within a metal as a single particle when the free electrons oscillate collectively under a specific condition. When a plasmon is locally confined to a surface, the plasmon is referred to as a surface plasmon.
A phenomenon in which, when light in the range from the visible band to the near-infrared band is incident on a metal surface, a surface plasmon is excited at a specific wavelength while an electric field constituting part of light is interacting with the surface plasmon is called surface plasmon resonance. This phenomenon forms a fundamental principle by which gold glitters in a unique gold color or a smooth metal surface sheds unique metallic luster.
In particular, when a surface plasmon is generated via strong interaction with a photon incident in a TM mode upon an interface between a thin metal film and a dielectric, a near field that propagates along the interface along with the surface plasmon appears. A surface wave attributable to the propagation of such a near field is treated as a single quasiparticle, and is referred to as a surface plasmon polariton (SPP).
Meanwhile, although light in the range from the visible band to the near-infrared band that is optically used in various ways generally has the advantages of high operating speed, wide bandwidth, incoherence, low loss, etc., problems with the level of integration and optical control must be overcome in order to actively use the light in the field of information technology. The problem with the level of integration arises from a fundamental limitation in which an optical wave cannot be focused within a range smaller than its wavelength, which is called the diffraction limit of light. Accordingly, in integrated optics, the limit of line width is in the range from 0.5 to 1 μm, which is significantly higher than the range from 10 to 100 nm range which can be achieved by state-of-the-art semiconductor technology.
In contrast, an SPP is capable of overcoming the diffraction limit of light because the energy of the optical wave of the SPP is highly focused within a range narrower than the wavelength of an optical wave incident from an interface between a thin metal film and a dielectric. Technology and the field of technology that deal with the implementation of devices for confining, propagating, transmitting and receiving, distributing, combining, reflecting, and filtering an SPP wave using the above-described characteristics are collectively called plasmonics.
However, plasmonics has experienced difficulties in implementing the generation, transmission and reception, transmission, duplication, amplification and switching of an SPP due to the unique rectilinear propagation property of the SPP.